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Rhamphomyia longicauda - female

Rhamphomyia longicauda - Female
Parkwood, Durham County, North Carolina, USA
May 20, 2005
Size: 10 mm
I've seen these in my back yard and at other nearby sites for the last couple of weeks. As they fly, the fringed legs are held out to the side, giving an odd effect. (This might be mimicry of lycid beetles--the outstretched legs resemble the spread elytra of a beetle, perhaps.) I finally got one to hold still and got photos. This one was perched quite still on some violets in the understory of the woods in my back yard. The time was 6:54 p.m. EST, approaching dusk. (Reference below indicates females swarm near dusk.) You can see the air sacks on the abdomen as well in this photo--see explanation below. Length was measured by photographing the leaf it was perched on next to a scale. Image updated 2/22/2020!

Identification based on other photos in the guide, for instance:

That photo is identified as a likely Rhamphomyia longicauda. See that photo for references on the interesting mating patterns of some members of the Empididae. In some species, this one apparently included, females form swarms and males chose desirable females. Females eat only the nuptial gifts provided by males. The fringe on the female legs, plus the inflated air sacks (visible in this photo) serve to mimic an abdomen filled with eggs. See, for instance: FEMALEMATING SWARMS INCREASE PREDATION RISK...

I might have caught a male of the same species at my porch light about ten days earlier:

Images of this individual: tag all
Rhamphomyia longicauda - female Rhamphomyia longicauda - female Rhamphomyia longicauda - female

Very interesting discussion. On the topic of mimicry
On the topic of mimicry, has anyone speculated that female R. longicauda are mimics of Assassin Bugs (Reduviidae)? I recently saw some R. longicauda females in the field, and that's what I thought they were at first. Or perhaps Leaf-footed Bugs (Coreidae)?

Moved from Rhamphomyia.

Thanks for the specific ID, Isaac. That's what we had all been thinking back when this was posted, but nobody had the expertise to be sure.
I had a number of these in my back yard back in 2005 (and maybe the next couple of years), but I have not seen them in recent years--too bad, as I would like to get more photos.

It is interesting how populations of so many creatures fluctuate through the years. Of course, casual observations are not enough; but I find them illustrative nonetheless.

This is another example of a photo that waited many years for a final ID. We should show it to those who get very impatient after a few days. I had a dance fly IDed just a few days ago. It had also been waiting for seven years. Thanks, Isaac for that one, too.

Very nice pictures, indeed. You are spot on with Rhamphomyia. I do not know about the longicauda, though. If you can get a lateral shot of the male and post it, I may check that for you.

About swarming:
1. You may have male swarms, female swarms and mixed swarms. In the case of the first two it may be that the other sex does not form swarms but joins the existing swarm for mate selection, or there are nearby separate swarms and specimens from one of those leave for the other to select a mate.
2. Different species swarm a different times of day. Some may swarm during the whole day, others maybe only for an hour at dusk, etc.
3. The location of the swarm is determined by markers. These may be very specific (under a overhanging branch in the sun, so the swarms may move with the sun) or rather 'generally defined' (along a slope, creating a very 'long' swarm, or over the water surface in a brook).
4. Nuptial gifts are not known for all mating dance flies. They are mostly found in the Empididae Empidinae (in genera like Empis, Rhamphomyia and Hilara) (the latter including the balloon flies).


Thanks for the info
Thanks to both of you for all this information. It is a lot better to know something besides the name of the creature in question; and there are so many things to learn!

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